Nehanjali Parmar

Nine isolates of Turnip mosaic potyvirus (TuMV)-infecting radish collected from different regions of Northern India were characterized. All isolates except for New Delhi and Rajasthan isolates resulted positive for TuMV in double antibody sandwich-enzyme linked immunosorbent assay (DAS-ELISA). RNA was isolated from leaves of infected plants and used in reverse transcriptase-polymerase chain reaction (RT-PCR) with TuMV coat protein (CP) gene-specific primers. Viral amplicons of expected 1000 bp size were obtained, which were further subjected to cloning and sequencing. CP gene of all the seven isolates was 867 bp long, encoding 288 amino acid residues. Percent homology of CP gene of all the Indian isolates among themselves and with other TuMV isolates retrieved from NCBI was in the range of 87-99 and 92-100% at nucleotide and amino acid levels, respectively. Phylogenetic analysis based upon CP gene nucleotide and amino acid sequences with other TuMV isolates reported from across the globe using unweighted pair group method with arithmetic mean (UPGMA) inferred classification of test isolates into basal-BR group due to their occurrence nearest to the TuMV isolates belonging to the basal-BR group. Information generated about the characteristic features of TuMV and geographical distribution of particular virus genotype-infecting radish crop will provide a platform for formulating disease resistance strategies.

Genetic engineering technique offers myriads of applications in improvement of horticultural crops for biotic and abiotic stress tolerance, and produce quality enhancement. During last two decades, a large number of transgenic horticultural crops has been developed and more are underway. A number of genes including natural and synthetic Cry genes, protease inhibitors, trypsin inhibitors and cystatin genes have been used to incorporate insect and nematode resistance. For providing protection against fungal and bacterial diseases, various genes like chitinase, glucanase, osmotin, defensin and pathogenesis-related genes are being transferred to many horticultural crops world over. RNAi technique has been found quite successful in inducing virus resistance in horticultural crops in addition to coat protein genes. Abiotic stresses such as drought, heat and salinity adversely affect production and productivity of horticultural crops and a number of genes encoding for biosynthesis of stress protecting compounds including mannitol, glycine betaine and heat shock proteins have been employed for abiotic stress tolerance besides various transcription factors like DREB1, MAPK, WRKY, etc. Antisense gene and RNAi technologies have revolutionized the pace of improvement of horticultural crops, particularly ornamentals for color modification, increasing shelf-life and reducing post-harvest losses. Precise genome editing tools, particularly CRISPR/Cas9, have been efficiently applied in tomato, petunia, citrus, grape, potato and apple for gene mutation, repression, activation and epigenome editing. This review provides comprehensive overview to draw the attention of researchers for better understanding of genetic engineering advancements in imparting biotic and abiotic stress tolerance as well as on improving various traits related to quality, texture, plant architecture modification, increasing shelf-life, etc. in different horticultural crops.

IndianJournals.com - Gateway to access, disperse and preserve knowledge!

A high frequency plant regeneration pro-tocol via direct organogenesis has been develo-ped for Punica granatum L. cv. Kandhari Kabuli, a medicinally important horticultural tree. Cotyle-don explants procured from 15-20-days-old in vitro grown seedlings were used as explants. MS medium supplemented with 2.0 mg/l 6-benzylaminopurine (BAP) and 1.5 mg/l naphtha-lene acetic acid (NAA) was optimal for shoot re-generation, which resulted into highest frequen-cy of shoot regeneration (67.89%) along with maximum average number of shoots formed per explant (5.38) and average shoot length (3.62 cm). Shoot multiplication and elongation took place on the same medium. Half strength MS medium containing 0.1 mg/l NAA and 0.02% ac-tivated charcoal was found most effective for rooting of shoots resulting into 80.12% root re-generation frequency. Regenerated plantlets were transferred to plastic cups containing auto-claved peat moss and successfully acclimatized with 85% survival rate. This is the first report on in vitro plant regeneration through direct orga-nogenesis in P. granatum L. cv. Kandhari Kabuli using cotyledon explants.